Regiochemistry and Stereochemistry of Intramolecular Photocycloaddition of Carbon-Carbon Double Bonds to Cyclohexenones

Article abstract of DOI:10.1021/jo00014a040

The intramolecular <2+2> photocycloaddition mechanism of alkenes tethered by a three-methylene chain to cyclohexenones has been studied.It was found that the reversion from a 1,4-diradical intermediate to starting material is slow relative to the rate of photoadduct formation.Only "straight" closure was observed in the systems studied.For compounds 1-3 and 5, the assumption that the first bond is formed between the β-carbon of the enone and C-4' leading to a 1,4-diradical is supported.For the formation of compounds 6-11, possible mechanisms are discussed.